Ocal, IT

Abstract Background: Patients achieving a pathologic complete response (pCR) following neoadjuvant therapy have significantly improved event-free survival relative to those who do not; and pCR is an FDA-accepted endpoint to support accelerated approval of novel agents/combinations in the neoadjuvant treatment of high risk early stage breast cancer. Previous studies have shown that recurrence risk increased with increasing burden of residual disease (as assessed by the RCB index). As well, these studies suggest that patients with minimum residual disease (RCB-I class) also have favorable outcomes (comparable to those achieving a pCR) within high risk tumor subtypes. In this study, we assess whether integrating RCB with MRI functional tumor volume (FTV), which in itself is prognostic, can improve prediction of distant recurrence free survival (DRFS); and identify a subset of patients with minimal residual disease with comparable DRFS as those who achieved a pCR. Imaging tools can then be used to identify the subset that will do well early and guide the timing of surgical therapy. Method: We performed a pooled analysis of 596 patients from the I-SPY2 TRIAL with RCB, pre-surgical MRI FTV data and known follow-up (median 2.5 years). We first assessed whether FTV predicts residual disease (pCR or pCR/RCB-I) using ROC analysis. We applied a power transformation to normalize the pre-surgical FTV distribution; and assessed its association with DRFS using a bi-variate Cox proportional hazard model adjusting for HR/HER2 subtype. We also fitted a bivariate Cox model of RCB index adjusting for subtype; and assessed whether adding pre-surgical FTV to this model further improves association with DRFS using a likelihood ratio (LR) test. For the Cox modeling, penalized splines approximation of the transformed FTV and RCB index with 2 degrees of freedom was used to allow for non-linear effects of FTV and RCB on DRFS. Result: Pre-surgical MRI FTV is significantly associated with DRFS (Wald p<0.00001), and more effective at predicting pCR/RCB-I than predicting pCR alone (AUC: 0.72 vs. 0.65). Larger pre-surgical FTV remains associated with worse DRFS adjusting for subtype (Wald p <0.00001). The RCB index is also significantly associated with DRFS adjusting for subtype (Wald p<0.00001). Adding FTV to a model containing RCB and subtype further improves association with DRFS (LR p=0.0007). RCB-I patients have excellent DRFS (94% at 3 years compared to 95% in the pCR group). Efforts are underway to identify an optimal threshold for dichotomizing pre-surgical FTV and FTV change measures for use in combination with pCR/RCB-I class to generate integrated RCB (iRCB) groups as a composite predictor of DRFS. Conclusion: Pre-surgical MRI FTV is effective at predicting minimal residual disease (RCB0/I) in the I-SPY 2 TRIAL. Despite the association between FTV and RCB, FTV appears to provide independent added prognostic value (to RCB and subtype), suggesting that integrating MRI volume measures and RCB into a composite predictor may improve DRFS prediction. Citation Format: Hylton NM, Symmans WF, Yau C, Li W, Hatzis C, Isaacs C, Albain KS, Chen Y-Y, Krings G, Wei S, Harada S, Datnow B, Fadare O, Klein M, Pambuccian S, Chen B, Adamson K, Sams S, Mhawech-Fauceglia P, Magliocco A, Feldman M, Rendi M, Sattar H, Zeck J, Ocal I, Tawfik O, Grasso LeBeau L, Sahoo S, Vinh T, Yang S, Adams A, Chien AJ, Ferero-Torres A, Stringer-Reasor E, Wallace A, Boughey JC, Ellis ED, Elias AD, Lang JE, Lu J, Han HS, Clark AS, Korde L, Nanda R, Northfelt DW, Khan QJ, Viscusi RK, Euhus DM, Edmiston KK, Chui SY, Kemmer K, Wood WC, Park JW, Liu MC, Olopade O, Tripathy D, Moulder SL, Rugo HS, Schwab R, Lo S, Helsten T, Beckwith H, Haugen PK, van't Veer LJ, Perlmutter J, Melisko ME, Wilson A, Peterson G, Asare AL, Buxton MB, Paoloni M, Clennell JL, Hirst GL, Singhrao R, Steeg K, Matthews JB, Sanil A, Berry SM, Abe H, Wolverton D, Crane EP, Ward KA, Nelson M, Niell BL, Oh K, Brandt KR, Bang DH, Ojeda-Fournier H, Eghtedari M, Sheth PA, Bernreuter WK, Umphrey H, Rosen MA, Dogan B, Yang W, Joe B, I-SPY 2 TRIAL Consortium, Yee D, Pusztai L, DeMichele A, Asare SM, Berry DA, Esserman LJ. Refining neoadjuvant predictors of three year distant metastasis free survival: Integrating volume change as measured by MRI with residual cancer burden [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P2-07-03.

Abstract OBJECTIVE: Currently, no study has assessed the performance of contrast-enhanced spectral mammography (CESM) in evaluating tumor response in breast cancer patients undergoing neoadjuvant systemic therapy (NST). This study aims to evaluate whether the accuracy of CESM is comparable to MRI in detection of residual breast cancer following NST. MATERIALS AND METHODS: Retrospective review of CESM cases at our institution between September 2014 and June 2016 identified patients who had both CESM and MRI pre- and post-NST with pathologic assessment after surgical management. Size of residual malignancy (if any) on post-neoadjuvant CESM and MRI was compared to surgical pathology (reference standard). Pathologic complete response (pCR) was documented and compared to Residual Cancer Burden (RCB) score for confirmation. Bland-Altman plots were used to visualize the differences between CESM/MRI and pathologic tumor size. RESULTS: Forty female patients met inclusion criteria. Mean age was 52.3 years (range 35-73). Type of NST included: 34 (85%) chemotherapy and 6 (15%) endocrine therapy. Histological analysis showed invasive ductal carcinoma in 38 (95%), the remaining cases consisted of one invasive lobular carcinoma, and one mixed invasive carcinoma. Mean tumor size after NST was 10.3 mm (range 0-75 mm) for CESM and 9.7 mm (range 0-60 mm) for MRI compared to 15.7 mm (range 0-100 mm) on final surgical pathology. Equivalence tests demonstrated that the mean tumor size measured by CESM or by MRI is equivalent to the mean tumor size measured by pathology within -1 and 1 cm range (p=0.0132 for CESM and p=0.0194 for MRI). Difference in Measurement Post-NST Compared to Pathology Path Tumor Size (mm)CESM Tumor Size (mm)MRI Tumor Size (mm)Mean (SD)15.7 (24.5)10.3 (18.9)9.7 (16.3)Difference Compared with Path (SD); P value -5.4 (12.6); 0.0132-6.0 (11.7); 0.0194 A complete radiologic response was seen in 25 CESM and 22 MRI cases which was confirmed by pathology in 17 and 14, respectively. Alternatively, CESM and MRI demonstrated residual disease in 15 patients and 18 patients respectively and this was confirmed on pathology in 15 and 15, respectively. Accuracy of CESM vs. MRIModalityResidual Disease by Pathology (N=23)Complete Response by Pathology (N=17)SensitivitySpecificityPPVNPVResidual Disease by CESM (N=15)150Complete Response by CESM (N=25)81765.2%100%100%68%Residual Disease by MRI (N=18)153Complete Response by MRI (N=22)81465.2%82.4%83.3%63.6% All patients who achieved a pCR had an RCB score of 0 indicating no residual cancer in lymph nodes. Among patients with residual disease, their mean RCB score was 2.6 (range 0.8-4.18). CONCLUSION: In this study, CESM was comparable to MRI in assessing residual malignancy after completion of NST, thereby offering a potentially faster and less expensive alternative to MRI for monitoring treatment response in the neoadjuvant setting. Citation Format: Hilal T, Covington M, Sugi M, Zhang N, Pockaj B, Northfelt D, Ocal IT, Patel BK. Contrast-enhanced spectral mammography is comparable to MRI in the assessment of residual breast cancer following neoadjuvant systemic therapy [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr PD2-11.

Abstract Introduction: The programmed cell death-1 (PD-1) immune checkpoint is a normal regulator of the autoimmune response to inflammatory stimuli. Several cancers have taken advantage of this mechanism by harboring its ligand (PD-L1), thus activating the checkpoint to evade immune destruction. Increased expression of PD-L1 on tumor cells has been linked with worse outcomes in several cancers, including breast cancer. In triple-negative breast cancer (TNBC), expression of PD-L1 is increased compared to luminal cancers and as such, has become a favorable target for anti-tumor therapies. However, few studies evaluate the impact of PD-1 and PD-L1 expression on overall survival (OS) in TNBC. The aim of this study was to assess OS based on PD-1 and PD-L1 positivity and distribution in the tumor microenvironment. Methods: All patients with newly diagnosed TNBC from 1999 to 2015 with adequate pathologic specimen were identified for evaluation. Surgical pathology specimens were stained by immunohistochemistry (IHC) for PD-1 and PD-L1. Those considered PD-1+ or PD-L1+ had a staining score of 3, 4, or 5. Patient and clinical characteristics of the adjuvant group were compared by PD-1 and PD-L1 status with Chi-Square and ANOVA, as appropriate; characteristics of the neoadjuvant population were described. OS was calculated using Kaplan-Meier method and compared by Log Rank test for PD-1, PD-L1 positivity and tumor microenvironment status. Results: Fifty-two patients met inclusion; 38 had surgery prior to chemotherapy while 14 had neoadjuvant chemotherapy. There were 15 PD-1+ patients (39%) and 21 PD-L1+ (55%) patients in the treatment naive cohort. No significant difference was found in the treatment naive group between age, race, postmenopausal status, final stage, or pathologic characteristics (e.g. tumor size, mitotic rate, and grade) for all PD-1+ and PD-L1+ patients. Of the 21 PD-L1+ patients, staining was present in the tumor, tumor/non-tumor (mixed), and non-tumor microenvironment 42.9%, 33.3%, and 23.8% of the time, respectively (p=0.008). No significant difference was found in OS between PD-1+ and PD-1- patients (p=0.509) or PD-L1+ and PD-L1- patients (p=0.240). However, distribution of PD-L1 staining significantly associated with OS. Those demonstrating PD-L1 staining in the tumor had a significantly higher OS than those with PD-L1 staining in the non-tumor microenvironment (p=0.008). In the subset of PD-L1+ patients, those with staining in the tumor show a 10-year OS of 100% versus 60% for those with staining in non-tumor (p=0.006). In the neoadjuvant cohort, 14.3% of patients expressed PD-1 positivity, while 42.9% had PD-L1 positivity; the distribution of the PD-L1 staining in tumor 14%, mixed 29%, and non-tumor 50%. No difference in OS was found based on PD-1 or PD-L1 (p=0.660) positivity in the neoadjuvant cohort. Conclusion: A large number of TNBC stain for PD-1 and/or PD-L1. The implications of this are yet to be determined. In this small cohort, pattern of staining had a significant impact on overall survival in treatment naïve patients. This finding will need to be validated on a larger cohort but may have important implications for treatment by defining patients who may benefit by checkpoint inhibitor therapy. Citation Format: Linnaus ME, Kosiorek H, Barrett MT, Dueck A, Anderson KS, Ocal IT, McCullough AE, Annamalai L, Yearley JH, Pockaj BA. Effect of PD-1 and PD-L1 in the tumor microenvironment on overall survival of triple-negative breast cancer patients [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr PD5-03.

Abstract Introduction: Previously, we detected amplification of chromosome 9p24.1 encoding PDL1, PDL2, and JAK2 (the PDJ amplicon) in up to 25% of triple negative breast cancers (TNBC) using oligonucleotide CGH arrays (aCGH). Amplification was associated with poor outcome and activation of the JAK/STAT pathway. Here, we have developed a novel fluorescence in situ hybridization (FISH) for detection of the JAK2/PDL1 amplification. Methods: We selected five 9p24.1-amplified and five non-amplified paraffin embedded TNBC tumor samples, defined by aCGH log2ratio>2.0 as amplified for FISH validation. 5' JAK2 DNA labeled with SpectrumGreen dUTP, 3' JAK2 DNA labeled in SpectrumOrange dUTP and a commercially available chromosome 9 centromeric probe (Spectrum Aqua) were combined as one probe set. The break-apart (BAP) probe set was applied to individual slides, hybridized, and washed, 50 events/sample were counted. We defined 9p24.1 amplification by FISH as the ratio of average JAK2 score/ average centromere 9 (CEN 9) score >1.1. Nonparametric student's t-test was used for statistical analysis. Results: In the amplified subgroup (n=5), JAK2 amplification was detected by FISH with the range from 1.89 to 21.0 (mean, 6.76). To adjust for aneuploidy, the ratio of JAK2 to CEN 9 was measured with the range from 1.02 to 9.21 (mean ratio, 2.9). The sample with highest level of amplification (aCGH log2ratio =4) detected by aCGH also scored highest by FISH (FISH ratio=9.21). One case with JAK2 amplification (aCGH log2ratio =3) was not detected by FISH (ratio, 1.02), but had low tumor cell content. In the non-amplification subgroup (n=5), JAK2 amplification was detected by FISH with the range from 0.98 to 3.54 (mean, 1.8), the ratio of JAK2 to CEN 9 was measured with the range from 0.48 to1.05 (mean, 0.73). Of note, two tumors with copy number loss by aCGH were confirmed by FISH (ratio 0.48, 0.56). In total, the 9p24.1 amplification was detected in 4 out 5 (80%) amplified samples defined by aCGH and 5 out 5 not amplified. A significant difference in JAK2: CEN 9 ratio (p=0.03) was observed between the amplified and non-amplified subgroups but not in JAK2 absolute scores (p=0.095). Conclusion: In this study, we have developed a novel FISH assay for detection of the 9p24.1 amplification in TNBC, encoding JAK2, PD-L1, and PD-L2. The FISH assay correlates with detection of the amplification by aCGH, but is less sensitive, in particular in tissue with lower tumor cell content. We predict that 9p24.1 amplification will be a clinically relevant biomarker in TNBC. Citation Format: Chen M, Andreozzi M, Pockaj B, Barrett MT, Ocal IT, McCullough AE, Anderson KS. A novel fluorescence in situ hybridization assay to detect 9p24.1 amplification in triple negative breast cancer [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P6-07-17.

Abstract Background: Triple negative breast cancer (TNBC) is a heterogeneous disease. Amplification of chromosome 9p24.1 encoding JAK2 and PD-L1 has been reported in up to 25% of TNBC and is associated with poor clinical outcome. In lymphoma, JAK2 is a transcriptional activator of both PD-1 ligands, and chromosome 9p copy number gain has been associated with therapeutic activity of nivolumab. We evaluated the interaction of JAK2 and PD-L1 expression in TNBC. Methods: 9p24.1 amplification in 4 TNBC cell lines (MDA-MB-231, MDA-MB-436, HCC1937, and HCC70) was measured using array comparative genomic hybridization (aCGH). Amplification was defined as aCGH log2ratio>2.0. Cell surface expression of PD-L1 was detected by flow cytometry and compared with the median fluorescence intensity (MFI) of isotype control Ig. To selectively inhibit JAK2, lentiviral vectors encoding two different shRNA were generated. JAK2, pSTAT1 and pSTAT3 expression were measured by immunoblot. The effects of the anti-JAK1/2 inhibitor ruxolitinib and interferon-gamma (IFN-γ) induction of PD-L1 was measured. Results: 9p24.1 copy number loss was measured in MDA-MB-231 (log2ratio =-1), neutral in HCC1937 ((log2ratio =0), gained in MDA-MB-436 ((log2ratio =+1) and amplified in HCC70 ((log2ratio =+2). No correlation was observed between PD-L1 expression and the 9p24.1 amplification, with the MFI ratio range from 5 to 16.5, mean 8.3 by flow cytometry. TNBC cell lines had higher baseline expression of PD-L1 compared to the ER+ cell lines T47D and MCF-7 (ratio, 0 p=0.1). Low dose IFN-γ (1.0-10.0 ng/ml) rapidly induced expression of PD-L1 in MDA-MB-231 (1.5 fold increase) and HCC70 (3.3 fold increase) with significant activation of the JAK2/STAT1 pathway. The induction of pSTAT1 and PD-L1 expression by IFN-γ was blocked with low dose (1mM) JAK1/2 inhibitor ruxolitinib. Knockdown of JAK2 with shRNA (>80%) did not impact PD-L1 baseline expression in MDA-MB-231 and HCC70 but abrogated IFN-γ –mediated induction of PD-L1 and the phosphorylation of STAT1. Conclusion: These data suggest that TNBC cell lines have baseline PD-L1 expression, but the cells with 9p24.1 amplification are highly sensitive to PD-L1 induction with IFN-γ which can be abrogated with inhibition with a JAK1/2 inhibitor or shRNA. Synergistic inhibition of PD1/PD-L1 and JAK2 may have therapeutic efficacy in the subset of TNBC with 9p24.1 amplification, and the dynamic effects of tumor PD-L1 expression in response to local inflammation should be considered in the evaluation of PD-1/PD-L1 checkpoint blockade. Citation Format: Chen M, Pockaj B, Andreozzi M, Barrett MT, Ocal IT, McCullough AE, Krishna S, Anderson KS. JAK2 and PD-L1 amplification enhance the dynamic expression of PD-L1 in triple negative breast cancer [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P2-04-18.

Abstract Introduction: Homologous recombination (HR) is essential for repairing double-stranded DNA breaks. Tumors deficient in DNA HR display high levels of copy number aberrations including amplifications, deletions, and breakpoints. Studies in BRCAmut cancers have shown that HR deficiency (HRD) renders triple negative breast carcinoma (TNBC) sensitive to carboplatin or Poly(ADP-ribose) polymerase (PARP) inhibitors via a synthetic lethal interaction, as previously described. Clinical observations in breast and other solid tumors suggest that the HRD phenotype may arise independently of BRCA1/2 mutation. The implications of HRD enrichment in PD-L1, PD-L2, Jak2 (PDJ) 9p24.1 amplified TNBC are not known. Our goal was to determine the HRD status in PDJ enriched tumors, and the potential association of the PDJ amplicon with a BRCA like HRD phenotype. Methods: Archival fresh frozen and formalin-fixed paraffin embedded (FFPE) tumor samples from 41 patients with TNBC were obtained from 1998-2015. Tumor populations (diploid, tetraploid, and aneuploidy) were sorted using DNA content flow cytometry and interrogated with oligonucleotide array comparative genomic hybridization (aCGH). Tumor homologous recombination deficiency (HRD) scores were calculated by number of interstitial aberrations (IA) in their genomes (HRD-IA). A cut-off of < 40 (low), > 40 (high) or > 50 (very high) was assigned based on our studies of known BRCAmut tumors. Data were compared between HRD groups using chi-square, ANOVA F-test or log-rank test. Results: 14/41 (34%) TNBC patients had high HRD-IA score and 6/41 (14.6%) had very high HRD-IA score. The median age was 61.8 years (SD = 12.8), the average tumor size was 3.1cm (SD = 2.6), 42% were node positive, 24% were pre-menopausal, 19% were Black, Hispanic, or Asian/Pacific Islander. Genetic testing was negative for BRCA1/2 mutations in 9/41 patients, including 3 high and very high HRD-IA score patients. There was no difference in the OS at 5-years [74% versus 59% (p = 0.907)] in the high HRD-AI group. 12/41 (29%) patients were PDJ+. In the PDJ+ patients, 4/12 (33.3%) had HRD > 40 and 1/12 (8.3%) had HRD > 50 compared to the PDJ- patients where 10/29 (34%) had high HRD-IA score and 5/29 (17%) had a very high HRD-IA score, p=0.463. Patients with inflammatory TNBC were significantly more likely to have high HRD-IA score 4/6 (66%) compared to non-inflammatory TNBC 8/31 (26%), p=0.05. Conclusions: We describe a unique group of TNBC patients with similar patient characteristics, tumor size, nodal status, and stage when compared by low, high and very high HRD-IA score. For inflammatory TNBC, there was statistically significant percentage of patients with a high HRD-IA score. We did not see a statistically significant correlation with 9p24.1 amplification based on HRD-IA score which has been suggested in other data sets. The HRD-IA score did not statistically impact OS but there was a suggestion that those with a higher score may have an improved OS potentially due to chemotherapy sensitivity. Further study with a greater number of patients to adequately power the study is needed to determine whether our initial findings can be confirmed and whether the HRD-IA score can be used to define a specific subset of TNBC patients. Citation Format: Gawryletz CD, Anderson KS, Northfelt DW, Kosiorek HE, Linnaus ME, Ocal IT, McCullough AE, Pockaj BA, Barrett MT. Homologous recombination deficiency in PD-L1, PD-L2, Jak2 (PDJ) amplified triple negative breast carcinoma [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P1-05-19.

Abstract Introduction: We have previously identified a 9p24.1 amplicon targeting PD-L1/JAK2 (PDJ) in subset (26.7%) of triple negative breast cancer (TNBC) patients. The PDJ amplicon is common in newly diagnosed and chemotherapy treated TNBCs and is associated with a worse prognosis. Our goal in this study was to determine whether immunohistochemistry (IHC) evaluation could identify those patients who harbor the PDJ amplicon. Methods: TNBC patients from 1999 to 2015 whose tumors were flow-sorted and evaluated by array-based comparative genomic hybridization (CGH) were identified; paraffin slides were obtained for IHC staining evaluation of JAK-2, phosphorylated STAT3 (pSTAT3), and PD-L1. Pathologic analysis consisted of scoring the stains for intensity (0-3+) and the relative percent of tumor cells with positive staining; positive score was defined as 3+ for any percent staining. Statistical analysis of IHC staining was performed to determine association with the PDJ amplicon defined by focal 9p24.1 copy number gain with CGH log2ratios of >1.0 for each sorted TNBC sample. Results: Eleven of 43 TNBC patients evaluable by IHC had the PDJ amplicon. There was no association between PDJ amplification and IHC staining for JAK-2, pSTAT3, or PD-L1 regardless of staining intensity or percentage tumor cells positive. Table 1 describes PDJ amplicon status and positivity for JAK2, pSTAT3 and PD-L1. Of PDJ-positive samples, 64%, stained positive for JAK2, 27% positive for pSTAT3, but 0% for PD-L1 in tumor cells. However, in the PDJ-negative group, 69% still stained positive for JAK2, 19% positive for pSTAT3, and 9% for PD-L1. Table 1: PDJ amplicon status and IHC staining JAK2 (3+) (n;%)pSTAT3 (3+) (n;%)PD-L1 (3+) (n;%)PDJ - (n=32)22;69%6;19%3;9%PDJ + (n=11)7;64%3;27%0;0% JAK2: Most PDJ-positive samples (10/11, 91%) showed some JAK-2 staining. Although one had only 1+ staining at 5% of the cells, the majority (7/11, 64%) had staining of 3+ and >10% of the cells with 2 patients demonstrating 3+ staining of 75% and 90% of the cells. However, those patients without the PDJ amplicon also exhibited JAK2 staining, with 66% (n= 22) of PDJ-negative cases staining strongly for JAK-2 (3+) and > 10% of cells. pSTAT3: All but one PDJ-positive case demonstrated some staining (1+ or greater) for pSTAT3; the staining intensity and percent positivity were much less than the JAK-2 staining with only 2 cases (18%) having 3+ staining of > 10%. Similar staining was seen in the PDJ-negative cohort; 75% of PDJ-negative patients had some pSTAT3 staining (1+ or greater) and 1 patient (5%) exhibited 3+ staining > 10%. PD-L1: Finally, the PD-L1 staining was low overall with only 18% of PDJ-positive cases demonstrating some staining for PD-L1. Notably, only one case stained 3+ with 20% positivity while the majority of the samples had a 2+ intensity encompassing 5-50% of the cells. Conclusions: IHC staining for JAK2, pSTAT3, or PD-L1 was not associated with the presence of the PDJ amplicon. Notably positive IHC staining for JAK2 was observed for both PDJ-positive and PDJ-negative tumor cells, thereby nullifying its application as a screening tool for PDJ amplification. Alternative methods, such as fluorescence in situ hybridization, are needed to identify PDJ-positive patients for further study. Citation Format: Linnaus ME, Kosiorek H, Ocal IT, Dixon L, Barrett MT, Gawryletz CD, Anderson KS, McCullough AE, McEachron TA, Pockaj BA. Immunohistochemistry cannot be used to detect PD-L1/JAK-2 amplification [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P1-03-13.

Abstract Introduction: Malignant phyllodes tumors are rare breast malignancies (0.1% of all breast tumors) with limited effective treatment options for recurrent and metastatic disease. Recent trials indicated a potential for anti-angiogenic therapy in soft tissue sarcomas, which led us to investigate these pathways. Materials and Methods: Thirty-five malignant phyllodes tumors (including two cases with matched primary and metastatic tumors) were profiled using gene sequencing (Next-generation and Sanger), gene copy number analysis (in-situ hybridization), whole genome RNA expression, and protein expression (immunohistochemical assay). Results: RNA microarray assay showed consistent over-expression of genes involved in angiogenesis including VEGFA, Angiopoietin2, VCAM1, PDGFRA, PTTG1, and CYP3A5 in all cases analyzed (n=5). No mutations in KDR (VEGFR2) were detected (0/26). EGFR protein overexpression was observed in 25/26 (96%) of cases with amplification of the EGFR gene in 8 cases (33%). EGFR gene mutations were identified in 2 cases (8%) including one case with presumed pathogenic V774M mutation and one case with EGFRvIII mutation. The most common mutations included those of TP53 (50%) and PIK3CA (15%) while other mutations (BRCA1, BRCA2, RET, CDH1, MLH1, ATM) were rare affecting single phyllodes cases. Two cases with matched primary and metastatic cancers harbored the same mutations in both sites (PIK3CA/KRAS and RB1 gene mutations, respectively). Conclusions: Comprehensive multiplatform profiling approach to phyllodes tumors identifies various molecular alterations of which some are potentially actionable. Our data suggests that anti-angiogenic therapy may also be effective in patients with malignant phyllodes tumor. Evaluation of EGFR pathway discovered consistent protein over-expression but rare activating mutations, which necessitates refinement in patient selection targeting these pathways. Citation Format: Gatalica Z, Vranic S, Ghazalpour A, Xiu J, Ocal I, McGill J, Bender R, Discianno E, Sanati S, Reddy S, Pockaj B. Comprehensive multiplatform molecular profiling identifies potentially targetable biomarkers in malignant phyllodes tumors of the breast. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P4-09-19.